Field of the Invention
This invention relates to C-clamps and more particularly, to an adjustable C-clamp which is characterized by a generally C-shaped clamp frame having a top frame segment, an intermediate frame segment and a bottom frame segment, which top and bottom frame segments are fitted with top and bottom clamp seats, respectively. A clamp cylinder is threaded in the top clamp seat substantially parallel to the intermediate frame segment. The clamp cylinder slidably receives a slotted cylinder which is secured in place typically by means of an alien screw, fitted in an allen screw receptacle approximately one-half of which extends through the clamp cylinder and the other half through the slotted cylinder. The slotted cylinder is characterized by a pair of parallel, diametrically-opposed longitudinal cylinder slots each of which communicates with a corresponding set of multiple, vertically spaced-apart, peripheral pin slots. A clamp rod is slidably extended through the bore of the slotted cylinder and is fitted with a pin opening for receiving a clamp rod pin. A clamp nut fitted to the extending end of the clamp rod faces the bottom clamp seat of the clamp frame. Manipulation of a clamp rod grip provided on the opposite end of the clamp rod from the clamp nut facilitates slidably adjustment of the clamp rod inside the slotted cylinder and the clamp cylinder as the clamp rod pin traverses the parallel longitudinal cylinder slots to align with a selected pair of pin slots. Twisting of the clamp rod typically in the clockwise direction as viewed from the clamp rod grip end facilitates movement of respective ends of the clamp rod pin into the pin slots and engagement of the clamp rod pin with the slotted cylinder. Accordingly, the clamp nut can be quickly positioned at a selected spacing from the bottom clamp seat to accommodate a workstock of selected width and thickness between the clamp nut and bottom clamp seat. Continued clockwise rotation of the clamp rod in the slotted cylinder facilitates threaded extension of the clamp cylinder through the top clamp seat of the clamp frame and incremental advancement of the clamp nut against the workstock to secure the workstock between the clamp nut and the bottom clamp seat. In another embodiment, the slotted cylinder is omitted and the longitudinal cylinder slots and respective sets of pin slots are milled, casted or otherwise provided in the bore wall of the clamp cylinder.
One of the problems inherent in conventional C-clamps is the frequent requirement that the threaded rod element be adjusted through the full range of threads in order to accommodate a fairly thick workstock and then adjusted through the same range of movement to accommodate a relatively thin workstock. There is no facility in the conventional C-clamp for quickly effecting an adjustment between a thin workstock and a thick workstock, and vice-versa.
C-clamps are extremely useful tools for various purposes in wood and metal work as they are quite easily used to clamp workstock of varying thicknesses to a workbench, work table or other fixed object and are commonly used for a variety of other purposes. However, the time and effort required to adjust from the thin workstock to the thick workstock and vice-versa, is objectionable and there exists a need in the art for an adjustable C-clamp for quickly and easily effecting this adjustment.